Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portionthereof with transitional graphical user interface showing our newdesign; and,

FIG. 2 is the second image thereof.

The outer perimeter broken lines show a display screen or portionthereof and forms no part of the claimed design.

The remaining broken lines in the figures depict portions of the displayscreen or portion thereof with transitional graphical user interfacewhich form no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-2. The process or period in whichone image transitions to another image forms no part of the claimeddesign.

CLAIM We claim the ornamental design for a display screen or portionthereof with transitional graphical user interface, as shown anddescribed.